MICAD (Molecular Imaging and Contrast Agent Database) is a searchable on-line collection of in vivo molecular imaging agents developed for positron emission tomography (PET), single photon emission computed tomography (SPECT), magnetic resonance imaging (MRI), ultrasound (US), computed tomography (CT), and optical imaging. MICAD, a key component of the "Molecular Libraries and Imaging" program of the NIH Roadmap, is being developed by NCBI, the National Center for Biotechnology Information.[unreadable] [unreadable] MICAD contains textual information, references, and numerous links to MEDLINE and additional resources including chemical structures in PubChem. Searches can be performed by entering one or more terms in the Search box (upper right). The links on the left provide additional information on MICAD, related resources, and guidelines for submitting agents to our database.[unreadable] [unreadable] Initial work has concentrated on techncial design and implementation of the authoring system used by MICAD curators. This is based on software developed for the NCBI Bookshelf and PubChem projects. Work has further concentrated on curator recruitment, training and standard operating procedures for authoring review-like chapters on molecular imaging agents. The project is now in production phase, with curators continuing to add new imaging agent chapters in an ongoing manner. As of September, 2006, over 160 chapters have been completed and released. MICAD shows usage by an average of over 100 users per day.